Energy & Momentum Flashcards

1
Q

Equation: Work done on an object by a constant force

A

W = F * d * cos(ø)
SI Unit = Joule = Newton * meter
Note: F = magnitude of force, d = mag of displacement, and ø = angle between force and displacement

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2
Q

Only the component of the force ________ the displacement is used to define work

A

along the displacement

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3
Q

In the absence of non-conservative forces (i.e. gravity), the work is independent of the _______.

A

Path taken

i.e. block lifted vertically or pushed up an inclined plane depends only on net vertical displacement

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4
Q

Equation: Kinetic Energy

A

KE = 1/2 * m * v^2

SI Unit = Joule (J)

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5
Q

Equation: Net Work done by ∆KE

A

W(net) = ∆KE = KE(f) - KE(o) = 1/2mv(f)^2 - 1/2mv(o)^2

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6
Q

Explains the amount of energy that an object of mass m has by virtue of its position relative to the surface of the earth. Position is measured by the height (h) of the object relative to an arbitrary zero level

A

work-energy theorem

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7
Q

Equation: Work-Energy Theorem

A

PE = mgh
Note: h = height above the earth
SI Unit = Joule (J)

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8
Q

Equation: Gravitational Potential Energy

A

PE = mgh

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9
Q

Defined as a change in the KE of a system

A

Work

SI Unit = Joule

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10
Q

Equation: Conservation of Energy

A

KE(i) + PE(i) = KE(f) + PE(f)

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11
Q

In the absence of forces like friction, mechanical energy is _______.

A

Conserved.

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12
Q

If the kinetic energy of an object increases by a certain amount, its potential energy ________.

A

Decreases by the same amount

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13
Q

the rate at which work is done

= work / time it took to perform the work

A

Power

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14
Q

Equation: Power

A

Power = Work / Time = W / t

SI Unit = Joule/second = Watt (W)

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15
Q

product of an object’s mass times its velocity
vector quantity that points in the same direction as velocity
conserved in the absence of an outside nonconservative force

A

momentum (p)

SI Unit = kg * m / sec

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16
Q

Equation : Momentum

A

p = m * v

SI Unit = kg * m / sec

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17
Q

a collision in which the total kinetic energy of the system after the collision is equal to the total kinetic energy before the collision

A

elastic collision

18
Q

Equation: Conservation of momentum

Applied to elastic collisions

A

(m1 * v1i) + (m2 * v2i) = (m1 * v1f) + (m2 * v2f)

19
Q

Collision in which the kinetic energy of the system is not conserved
collision in which the total KE of the system is not the same before and after the collision

A

inelastic collision

20
Q

collision in which objects collide and stick together

A

completely inelastic collision

21
Q

Equation: Conservation of Momentum for Completely Inelastic collisions

A

m1 * v1(i) + m2 * v2(i) = (m1 + m2) * v(f)

22
Q

In collision equations, make sure to account for the ________ of each momentum, which is a vector quantity.

A

direction

*If objects are moving toward each other, one velocity vector will be positive and one will be negative

23
Q

springs exhibit ______ behavior

24
Q

Equation: Hooke’s Law

A

F(restoring) = -k * x
SI Unit: N / m
Note: -k = spring constant (proportionality constant)
x = displacement of the spring from its unstrained length

25
described by Hooke's law | always points in a direction opposite to the displacement of the spring
restoring force
26
spring constant / proportionality constant describes stiffness of the spring higher the value of this, the harder it is to stretch or compress the spring
k (-k in Hooke's law equation)
27
maximum displacement from equilibrium
amplitude
28
for any object in simple harmonic motion, the time required to complete one cycle is called the ______
Period (T)
29
number of cycles of motion per second inverse of period (T) measured in Hertz = 1 / sec
Frequency (f)
30
Equation: Frequency
Frequency (f) = 1 / T | SI Unit: 1 / sec
31
frequency at which object of mass m vibrates on a spring | expressed in radians per second
angular frequency (omega)
32
Equation: Angular Frequency
``` angular frequency (omega) = 2 * π / T = 2 * π * f = √(k/m) SI unit = Radians / second ```
33
energy that a spring has because of being stretched or compressed
elastic potential energy (PE elastic)
34
Equation: Elastic Potential Energy: PE (elastic)
PE(elastic) = 1/2 * k * x^2 | SI Unit = Joule
35
at max displacement from equilibrium, the PE of the spring is at a ________ and the KE is _________
``` PE = maximum KE = 0 ```
36
total mechanical energy is conserved when nonconservative forces do no work
conservation of mechanical energy
37
Equation: Conservation of Mechanical Energy
E(f) = E(i)
38
Equation: Total Mechanical Energy
E(total) = 1/2mv^2 + mgh + 1/2kx^2 | SI Unit = Joule
39
Equation: Angular Freqency
``` Angular Frequency (omega) = 2πf = √(g/L) Note: g = 10 m/s^2 and L = length (m) ```
40
The PE of a mass at its equilibrium position =
0